Cigarette filters, incorporating various materials that mechanically, chemically and/or physically remove components of mainstream cigarette smoke have the disadvantage of non-selectively filtering components from mainstream smoke, even those components that contribute to flavor. The result may be a cigarette with an unsatisfactory taste.
For instance, carbon has been used to filter various components from mainstream smoke. Several modified forms of activated carbon has also been described, for example, in U.S. Pat. Nos. 5,705,269; 4,062,368; 3,652,461; 3,217,715; and 3,091,550. In addition, U.S. Pat. No. 6,117,810 describes activated carbon having zeolite salts crystallized in the pores. However, achieving the desired selectivity can be difficult. In addition, the production of such modified activated carbon typically requires additional processing steps, such as coating the activated carbon with solutions, filtration, drying and/or crystallization. Further, such methods are generally unsuitable to effectively impregnate the adsorbent material, and thus do not penetrate the pores or interior surfaces.
Thus, despite various developments in adsorbent and filtration materials, what is needed in the art are effective and inexpensive means for producing modified adsorbents, particularly those suitable for use in smoking articles and cigarette filters. Preferably, such adsorbents should preferentially remove selected components from mainstream tobacco smoke, while maintaining other components, such as those that contribute to flavor, for example. In particular, such adsorbent materials should preferentially adsorb selected components such as acrolein, hydrogen cyanide and acrylonitrile.